Method of making vessels



Nov. 14, 1944. v K G I Q -Z,362,544

METHOD OF MAKING VESSELS Filed Dec. 12, 1941 2 Sheets-Sheet 1 Arvi dRalphEckberg INVENT OR BY mafia/W ATTORNEY Nov. 14, 1944. A. R. ECKBERG'I METHOD OF MAKING VESSELS Filed Dec. 12, 1941 2 Sheets-Sheet Flux Fig.5.

- Nickel 13 Fl' .6. Silver g Fig. 10.

Arvid Ral h Eckberg INVENTOR ATTORNEY Patented Nov. 14, 1944 mz'rnon orm ne. vEssaLs Arvid Ralph Eckberg, Rochester, N. Y., assignor to EastmanKodak Company, Rochester, N. Y., a corporation of New Jersey ApplicationDecember 12, 1941, Serial No. 422,689

1 Claim. (6129-1483) This invention relates to material for vessels, andparticularly kettles and like apparatus employed in the mixing andheating of gelatin-base emulsions used as light-sensitive coatings onphotographic goods such as film, plates and paper, and to the methods offabricating such vessels in order to obtain the desired results from thespecial materials which have been found most suitable for such service.

In the manufacture of photographic emulsions it is vitally necessarythat all vessels, piping, mixing equipment and any other articles withwhich the emulsions may come in contact be absolutely free from anymetallic compounds or foreign particles that might contaminate thesensitive materials in the mixture, and cleaning of such apparatus ishighly specialized work of a painstaking nature.

It has been common practice heretofore to fabricate the cooking kettles,mixer blades, etc. of copper and then to electroplate with pure silverall surfaces that will be touched by the emulsion. Piping and fittingsare usually made of pure cast or drawn silver, as this has been found tobe the only metal suitable for the purpose.

In any plating operation, for instance on the inner surfaces of avessel, the silver is plated on in a plurality of deposits which areentirely flocculent in structure, and having in no way any parallelgrain or fiber-like form that would tend to give the silver inherentstrength and density. Consequently, minute particles of the silverplating occasionally flake off when the kettle is used or is beingcleaned. These particles may become mixed-with the emulsion, andalthough the latter contains salts of silver in quantity, neverthelesseven microscopic specks of pure metallic silver from the plating on thekettle or other parts constitute an impurity and an imperfection that isfully as objectionable as dirt or other foreign matter in the finishedsensitized products, especially in motion-picture film.

It has long been the practice of builders of silv r-lined vessels toattempt a more-or-less makeshift rolling of the plated-on lining,whereby with the use of wood or composition rollers, the silver is tosome extent compressed or "ironed down" between successive platings.This does serve to density the plated deposits, but because of thegranular structure thereof has a tendency to make the silver verybrittle, and it may shed rather large flakes or even break awayentirely, leaving the base metal exposed to contact with the emulsion.

The present invention contemplates a construe.

tion wherein electrodeposition of silver is entirely abandoned, and abimetallic rolled plate is formed to the required shape and thenfinished by a suitable welding technique that has been developed forthis specific purpose. By this method the inherent strength andhomogeneity of a rolled sheet is fully preserved, and any flaking off ispractically eliminated. The drawings herewith illustrate a specificexample of one type of emulsion vessel that may be constructedadvantageously from the materials and by the fabricating methodsconstituting this invention, and also details thereof at differentstages. In these drawings:

Fig. 1 is a top plan of a jacketed vessel constructed in accordance withthis invention;

Fig. 2 is a vertical section on line 2-2 of Fig. 1;

Figs. 3 and 4 are enlarged sections of details;

Fig. 5 is a cross section of a bi-metallic billet before rolling;

Fig. 6 is the same after rolling to the required thickness;

Figs. '7, 8 and 9 are fragmentary sections of the bimetallic sheetsduring various stages in the welding operation;

Fig. 10 is a vertical section, diagrammatic, of a forming operation; and

Fig. 11 is a perspective view of a formed detail.

- The basic feature of the present invention, and

the prime factor in the successful fabrication of vessels which will besatisfactory for the mixing and storage of photographic emulsions, is abimetallic sheet, consisting of a roiled sheet of pure silver suitablyattached to a similar sheet of an-' other and preferably tougher metal;so that the two will be inseparable while undergoing any reasonableforming and bending operations, and which may be welded by suitablemethods into a lasting and smooth surfaced structure of the requisitestrength.

Inasmuch as silver alon is of low tensile strength and easily bent,although of high duetility, it must be associated with a stronger mate,-rial for the purposes above mentioned. Such a suitable metal is purenickel, as it has the required tensile strength, is fairly ductile, isnoncorrosive and not easily oxidized, and when properly annealed willstand great deformation without fracture.

Material for use as above set forth is preferably mad up in the form ofthin billets as indicated in Fig. 5. It has been found that sheets inwhich the silver Ill and the nickel II are each approximately /2 inchthick may be obtained, up to an area of about 5 square feet. These areheated and hydraulically pressed together with a suitable flux l2between, and the edges are soldered with a special solder, as indicatedat l3. This composite billet is again heated to 1100-1200 F. and passedthrough suitable rolling apparatus until it has been reduced to a totalthickness of M; inch, that is, the silver and the nickel are then eachapproximately 1*; inch thick.

As the last part of the rolling is done with the metals practicallycold, the silver is very much compressed and densifled so that it willnot be inclined to flake. The resulting sheet may be slightly wavy, andif so may be again heated and flattened in suitable rolls. There appearsto be no tendency for the two sheets to separate during the rolling andpressing; in fact, this working serves to cause them to adhere morecompletely, so that the whole becomes, in eflect, a sheet of silver-cladnickel. The rolling has a tendency to homogenize and work harden thesilver, leaving it with a tougher and more fibrous structure than it hadin the bill't. The sheet (Fig. 6) is then ready for fabricating.

To construct the vessel shown in Figs. 1 to 4, several sheets may berequired, and this involves a welding technique which will be presentlydescribed. As nickel and silver have widely dif-' ferent melting points,(approximately 2640 and 1760 F. respectively), it will be apparent thatwelding presents a number of difliculties. Furthermore, nickel beingcomparatively hard, the sheets must be annealed at intervals when beingbent or formed. The annealing temperature should not exceed 1300 F.

Tomake a weld, two of the composite sheets are laid with their edgesclose together, nickel side uppermost, and the nickel is tack-welded.These welds are then ground smooth, and the remainder of the nickel weldis completed as at I4, Fig. 7, using an electric arc and a nickelelectrode with suitable protection against oxidation. After grinding theentire nickel weld smooth, the operator works on the silver side of thesheet, first using a narrow chisel with 9. diamond point and cleans outthe silver along the joint, forming a channel as at !5, Fig. 8. Thenthis channel is filled in with pure silver, using the atomic hydrogenwelding process for accurate control. During this welding of the silver,9. heavy metal block B is held in contact with the nickel side of thesheet to carry off excess heat so that it will not accumulate in thenickel and melt too much of the'silver because of the lower meltingpoint of the latter. erator to avoid undue heating of the nickel, sothat no nickel will bubble up through the silver and be present as anexposed inclusion in the finished silver surface. This precaution isvery important as nickel also may be harmful in contact with emulsion.The resulting fill, indicated at It in Fig. 9, may be ground smooth andpolished. It is not absolutely necessary to have a metal block incontact with the silver side of the sheet when welding the nickelbecause of the greater heat conductivity of the silver, although in somecases this may be done as an added precaution.

In Figs. 1 and 2 a vessel is illustrated which is of "bath-tub form ornon-circular, and therefore presents rather awkward difliculties infabri-' cation from the composite, silver-nickel sheets. The top flangeis simple'to form, as it may be This helps the op- 'weldsat 3i! and 31.

hand-hammered or bent on a bending brake." The bottom corners have beenfound to be most readily made as follows: A sheet is of suitable size iscut with rounded corners and is laid on a form 20, projecting beyond thesides of the form all around. A rectangular frame member 2| carried by ahydraulic press is then brought down and draws sheet l8 to the contourof the form 2@ as indicated in broken lines Fig. 10. It has been foundthat two to three anneals are required between partial draws and whencom-- pletely drawn the part resembles a dish, see Fig. 11. This pieceis then sawed or torch out into quarters 22, as indicated, and eachquarter is then used as a bottom corner of the vessel, and is welded tothe sides and ends as indicated in Fig. 2.

as emulsion -mixing vessels are usually jacketed, the presentembodimentis thus shown, the inner vessel 25 is indicated as composed of a mainside-and-bottom sheet 26, end sheets 21, all of which have anoutstanding flange 28, and the above-described bottom corner pieces 22,with A thick flange reinforcement 32 (Fig. 3) is welded to the nickelsheet at 33, while a similar part 84 is welded at 35 to the upper rim ofthe jacket 28. The jacket is preferably of non-corrosive material, suchas stainless steel or Monel metal.

A typical form of outlet, such as may be provided for a thermometer, isshown in Fig. 4. A ferrule 40, welded to the nickel sheet at 4!, isinternally threaded to receive a hollow silver plug 42, the compositesheet being swaged out and belied at 43, so that it may be drawnliquid-tight. A silver pipe 44 may be passed through the jacket 36 andpacked between clamp nuts 45. These examples of inlets and jacketconnections are presented as merely typical, and it is to be understoodthat many variations are posible in accordance with specificrequirements in service.

Emulsion vesels are frequently of circular form, with a dished bottomhead. These are not illustrated herewith, as they present no unusualdifflculties in fabrication, the shell being rolled in the usual mannerand the head being heated and formed in a press. The head may be dishedby spinning, if properly annealed. The drawings also do not indicate anymixing devices, as either built-in or detachable mixers may be used, andthese form no part of this invention.

The invention in its broadest aspects is not limited to the constructionof kettles or vessels as above described, but may be applied inconnection with other apparatus used in the photo-ma terials or chemicalindustries, such as evaporating trays, stirring paddles, driers, etc.

Having now particularly described my invention. what I desire to secureby Letters Patent of the United States and what I claim is:

A method of fabricating a vessel in which photographic emulsions areheated and agitated which comprises bonding-sheets of rolled nickel andsilver by hot working to produce a bi-metallic sheet of non-granularstructure, forming the sheets to required shapes mechanically includingsuitable anneals, assembling the formed sheets in position, the silversides being innermost, arcwelding with nickel the edges of the nickelportions, and gas welding with silver the edges of the silver portions.

ARVID RALPH ECKBERG.

